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71.
A total synthesis of (-)steganone, correlating it with L-glutamic acid, shows it to have the opposite configuration to that assigned by Kupchan. 相似文献
72.
B. S. Thyagarajan Phillip E. Glaspy Peter Brown 《Journal of mass spectrometry : JMS》1980,15(1):22-30
The title compounds display unusual modes of fragmentation under electron impact. One of the dominant modes is the concerted elimination of the two arylthio and arylsulfonyl moieties followed by further extrusion of the C6H4 unit as a cumulene. No elimination of SO2 is observed from any of the sulfones nor an expulsion of the C4H4 fragment. Such behavior contrasts strikingly with that of 1,4-diarylsulfonyl-2-butynes and of the 1,6-diarylsulfonyl-2,4-hexadiynes. 相似文献
73.
Karen V. Baker John M. Brown Neil A. Cooley Gareth D. Hughes Richard J. Taylor 《Journal of organometallic chemistry》1989,370(1-3):397-406
The palladium dibromide complexes of (S,R)-(1,1′-bis-diphenylphosphino)-2-ferrocencylthyldimethylamine and (S,R)-(1-diphenylphosphino)-2-ferrocenylethyldimethylamine have been reduced with dilithiocyclooctatetraene to form the corresponding Pd0 cyclooctatetraene complexes. Their reactions with E-4-methoxy-2′-bromophenylethene, and then benzylmagnesium chloride at −60 to −30°C, provide information on the structure of intermediates in asymmetric cross-coupling. 相似文献
74.
J. R. Brown J. H. O'Donnell 《Journal of polymer science. Part A, Polymer chemistry》1972,10(7):1997-2004
Mixtures of sulphur dioxide and butene-1 have been polymerized in the gas phase to the 1:1 alternating copolymer by electron irradiation. The rate of polymerization, measured by the decrease in gas pressure, decreased with increase in temperature over the range ?20 to +30°C. The initial G(-monomer) values decreased from 500 to 50 giving an Arrhenius activation energy of ?30 kJ mol?1. These results are consistent with a ceiling temperature-pressure relationship. The ceiling temperature is about 60°C lower than that observed previously in the liquid phase in accord with thermo-dynamic prediction. 相似文献
75.
Establishing a calibration model is an important part of any mathematical method for multi-component determination. Use of a calibration model based on single spectra is subject to error, because the model spectrum chosen may not be representative of the response over the full range of the calibration. Alternative calibration models require more time to establish calibration, an these may not be convenient for real-time determinations. A novel calibration method is reported for use with Kalman filters. The method, dynamic modeling, is based on the use of libraries of calibration spectra. The set of used to describe the model at any time is based on component concentrations, estimated for the multi-component mixture, as determined from the Kalman filter, so that several spectra can be used to best describe a varying response. Through application of the dynamic modelingt to simulated and real chromatograms, it is demonstrated that use of the method decreases estimation errors cause by model data mismatches, and that full benefit can be obtained from relatively small libraries. 相似文献
76.
M.Mark Midland Ronald L. Halterman Charles A. Brown Angela Yamaichi 《Tetrahedron letters》1981,22(42):4171-4172
The isomerization of optically-active secondary propargyl alcohols, RCHOHCC(CH2)nCH3, to terminal acetylenic alcohols, RCHOH(CH2)n+1 C=CH, by potassium 3-aminopropylamide (KAPA) proceeds without loss of configuration at the hydroxy center. 相似文献
77.
The total synthesis is described of (±) 6-(7-carboxy hept-1-yl) 3-hydroxy 2-methyl piperidine [(±) carpamic acid] in five steps from 1-ethoxycarbonyl 6-methyl hept-5-en-2-one. 相似文献
78.
Glassy carbon electrodes modified with (5-amino-1,10-phenanthroline)bis(bipyridine)ruthium(II) chloride hydrate, [(bpy)2Ru(5-phenNH2)]Cl2·H2O, are shown to oxidize hydrazine with excellent sensitivity. The presence of an amine group on the ruthenium complex facilitates electropolymerization onto the electrode surface. Using cyclic voltammetry, a large catalytic current is observed upon oxidation of hydrazine in phosphate buffer (pH 5.0), compared to the current obtained from the ruthenium-modified electrode with no hydrazine present. The sensitivity of cyclic voltammetry is sufficient for obtaining a linear calibration curve for hydrazine over the range of 10−5 to 10−2 M. Hydrodynamic amperometry was used to determine the working potential for flow injection analysis. The limit of detection for hydrazine was determined to be 8.5 μM using FIA. The thickness of these films was shown to increase linearly with the number of electropolymerization cycles, in the range of 1000-2500 nm for 5-20 cycles, respectively, using Rutherford backscattering spectrometry (RBS). RBS analysis also suggests that the film is multilayered with the outermost layers containing a high ruthenium concentration, followed by layers where the concentration of ruthenium decreases linearly and approaches zero at the electrode surface. 相似文献
79.
Subramaniam V Alves ID Salgado GF Lau PW Wysocki RJ Salamon Z Tollin G Hruby VJ Brown MF Saavedra SS 《Journal of the American Chemical Society》2005,127(15):5320-5321
Transmembrane proteins (TMPs), particularly ion channels and receptors, play key roles in transport and signal transduction. Many of these proteins are pharmacologically important and therefore targets for drug discovery. TMPs can be reconstituted in planar-supported lipid bilayers (PSLBs), which has led to development of TMP-based biosensors and biochips. However, PSLBs composed of natural lipids lack the high stability desired for many technological applications. One strategy is to use synthetic lipid monomers that can be polymerized to form robust bilayers. A key question is how lipid polymerization affects TMP structure and activity. In this study, we have examined the effects of UV polymerization of bis-Sorbylphosphatidylcholine (bis-SorbPC) on the photoactivation of reconstituted bovine rhodopsin (Rho), a model G-protein-coupled receptor. Plasmon-waveguide resonance spectroscopy (PWR) was used to compare the degree of Rho incorporation and activation in fluid and poly(lipid) PSLBs. The results show that reconstitution of Rho into a supported lipid bilayer composed only of bis-SorbPC, followed by photoinduced lipid cross-linking, does not measurably diminish protein function. 相似文献
80.
R. Anil Rugunanan Michael E. Brown 《Journal of Thermal Analysis and Calorimetry》1991,37(6):1193-1211
Thermogravimetry (TG) and differential scanning calorimetry (DSC) have been used to examine the thermal behaviour, in N2 and in air, of the Si/Sb2O3, Si/KNO3, Si/Fe2O3 and Si/SnO2 pyrotechnic systems, in relation to the behaviour of the individual constituents.TG curves for Si powder, heated alone in air, showed that limited oxidation of Si occurred above 700°. In N2, Sb2O3 sublimed completely between 500 and 900° and, in air, sublimation was accompanied by oxidation to Sb2O4. The Sb2O4 decomposed at higher temperatures. DSC curves for KNO3 heated in N2 showed the usual crystalline transition and melting endotherms followed by endothermic decomposition between 400 and 950°. DSC and TG curves of SnO2and Fe2O3 revealed no thermal events when samples were heated to 1000° in either N2 or air.For the Si/Sb2O3 system, the oxidation of Si by Sb2O3 between 590 and 700°, was complicated by sublimation of Sb2O3 in N2 and also by the oxidation of Sb2O3 in air. No thermal events were observed for the Si/SnO2and Si/Fe2O3 systems when heated under a variety of conditions in either N2 or in air, although these systems do sustain combustion on suitable ignition. In the Si/KNO3 system, oxidation of Si occurs in a KNO3 melt at temperatures above 560° in nitrogen and in air.
Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60th birthday 相似文献
Zusammenfassung Mittels TG und DSC wurde das thermische Verhalten der pyrotechnischen Systeme Si/Sb2O3, Si/KNO3, Si/Fe2O3 und Si/SnO2in N2 und in Luft im Vergleich zum Verhalten der einzelnen Komponenten untersucht.TG-Aufnahmen über das Erhitzen von Si-Pulver in Luft zeigten eine begrenzte Oxidation von Silizium oberhalb 700°C. Sb2O3 sublimiert in Stickstoff vollständig zwischen 500 und 900°C, in Luft wird die Sublimation durch Oxidation zu Sb2O4 begleitet. Sb2O4 zersetzt sich bei höheren Temperaturen. DSC-Aufnahmen für KNO3 in N2 zeigen die gewohnten Umwandlungs- und Schmelzendothermen, gefolgt von einer endothermen Zersetzung zwischen 400 und 950°C. Die DSC- und TG-Kurven für SnO2und Fe2O3 zeigen bei Erhitzen bis 1000°C weder in N2 noch in Luft den Verlauf thermische Prozesse an.Bei dem System Si/Sb2O3 spielt sich neben der Oxidation von Si durch Sb2O3 zwischen 590 und 700°C auch eine Sublimation von Sb2O3 in N2 sowie eine Oxidation von Sb2O3 in Luft ab. Für die Systeme Si/SnO2und Si/Fe2O3 konnten durch Erhitzen unter einer Reihe von Bedingungen weder in Luft noch in N2 Thermoprozesse nachgewiesen werden, obwohl diese Systeme nach geeigneter Zündung den Brennvorgang aufrechterhalten. Im System Si/KNO3 erfolgt sowohl in N2 als auch in Luft oberhalb 560°C die Oxidation von Si in der KNO3-Schmelze.
Dedicated to Professor Dr. H. J. Seifert on the occasion of his 60th birthday 相似文献